I guess I'm also ignorant about how Github works. If I go to one of the MiniCore link or MCUdude link and find the right .hex file, right-click on that and save it, what I get is source code. It still has a .hex extension, but it's source code, about 74K. So to get the actual .hex file, I had to left-click on the file, which makes the actual .hex file text be displayed in the text box below, then copy and paste that into a .hex file.

I'm sure I'm doing something wrong, but it's really confusing that right-click and save-as doesn't give you the file you right-clicked on. Anyway, I have the v8 .hex file now, so thanks to everyone for the links.